/*
 * Copyright (C) 2009 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#define LOG_TAG "backup_data"

#include <stdio.h>
#include <string.h>
#include <unistd.h>

#include <androidfw/BackupHelpers.h>
#include <utils/ByteOrder.h>

namespace android {

    static const bool kIsDebug = false;

/*
 * File Format (v1):
 *
 * All ints are stored little-endian.
 *
 *  - An app_header_v1 struct.
 *  - The name of the package, utf-8, null terminated, padded to 4-byte boundary.
 *  - A sequence of zero or more key/value paires (entities), each with
 *      - A entity_header_v1 struct
 *      - The key, utf-8, null terminated, padded to 4-byte boundary.
 *      - The value, padded to 4 byte boundary
 */

    const static int ROUND_UP[4] = {0, 3, 2, 1};

    static inline size_t
    padding_extra(size_t n) {
        return ROUND_UP[n % 4];
    }

    BackupDataWriter::BackupDataWriter(int fd)
            : m_fd(fd),
              m_status(NO_ERROR),
              m_entityCount(0) {
        m_pos = (ssize_t) lseek(fd, 0, SEEK_CUR);
        if (kIsDebug) LOGI("BackupDataWriter(%d) @ %ld", fd, (long) m_pos);
    }

    BackupDataWriter::~BackupDataWriter() {
    }

// Pad out anything they've previously written to the next 4 byte boundary.
    status_t
    BackupDataWriter::write_padding_for(int n) {
        ssize_t amt;
        ssize_t paddingSize;

        paddingSize = padding_extra(n);
        if (paddingSize > 0) {
            uint32_t padding = 0xbcbcbcbc;
            if (kIsDebug) LOGI("writing %zd padding bytes for %d", paddingSize, n);
            amt = write(m_fd, &padding, paddingSize);
            if (amt != paddingSize) {
                m_status = errno;
                return m_status;
            }
            m_pos += amt;
        }
        return NO_ERROR;
    }

    status_t
    BackupDataWriter::WriteEntityHeader(const String8 &key, size_t dataSize) {
        if (m_status != NO_ERROR) {
            return m_status;
        }

        ssize_t amt;

        amt = write_padding_for(m_pos);
        if (amt != 0) {
            return amt;
        }

        String8 k;
        if (m_keyPrefix.length() > 0) {
            k = m_keyPrefix;
            k += ":";
            k += key;
        } else {
            k = key;
        }
        if (kIsDebug) {
            ALOGD("Writing header: prefix='%s' key='%s' dataSize=%zu", m_keyPrefix.string(),
                  key.string(), dataSize);
        }

        entity_header_v1 header;
        ssize_t keyLen;

        keyLen = k.length();

        header.type = tolel(BACKUP_HEADER_ENTITY_V1);
        header.keyLen = tolel(keyLen);
        header.dataSize = tolel(dataSize);

        if (kIsDebug) LOGI("writing entity header, %zu bytes", sizeof(entity_header_v1));
        amt = write(m_fd, &header, sizeof(entity_header_v1));
        if (amt != sizeof(entity_header_v1)) {
            m_status = errno;
            return m_status;
        }
        m_pos += amt;

        if (kIsDebug) LOGI("writing entity header key, %zd bytes", keyLen + 1);
        amt = write(m_fd, k.string(), keyLen + 1);
        if (amt != keyLen + 1) {
            m_status = errno;
            return m_status;
        }
        m_pos += amt;

        amt = write_padding_for(keyLen + 1);

        m_entityCount++;

        return amt;
    }

    status_t
    BackupDataWriter::WriteEntityData(const void *data, size_t size) {
        if (kIsDebug) ALOGD("Writing data: size=%lu", (unsigned long) size);

        if (m_status != NO_ERROR) {
            if (kIsDebug) {
                ALOGD("Not writing data - stream in error state %d (%s)", m_status,
                      strerror(m_status));
            }
            return m_status;
        }

        // We don't write padding here, because they're allowed to call this several
        // times with smaller buffers.  We write it at the end of WriteEntityHeader
        // instead.
        ssize_t amt = write(m_fd, data, size);
        if (amt != (ssize_t) size) {
            m_status = errno;
            if (kIsDebug) ALOGD("write returned error %d (%s)", m_status, strerror(m_status));
            return m_status;
        }
        m_pos += amt;
        return NO_ERROR;
    }

    void
    BackupDataWriter::SetKeyPrefix(const String8 &keyPrefix) {
        m_keyPrefix = keyPrefix;
    }


    BackupDataReader::BackupDataReader(int fd)
            : m_fd(fd),
              m_done(false),
              m_status(NO_ERROR),
              m_entityCount(0) {
        memset(&m_header, 0, sizeof(m_header));
        m_pos = (ssize_t) lseek(fd, 0, SEEK_CUR);
        if (kIsDebug) LOGI("BackupDataReader(%d) @ %ld", fd, (long) m_pos);
    }

    BackupDataReader::~BackupDataReader() {
    }

    status_t
    BackupDataReader::Status() {
        return m_status;
    }

#define CHECK_SIZE(actual, expected) \
    do { \
        if ((actual) != (expected)) { \
            if ((actual) == 0) { \
                m_status = EIO; \
                m_done = true; \
            } else { \
                m_status = errno; \
                ALOGD("CHECK_SIZE(a=%ld e=%ld) failed at line %d m_status='%s'", \
                    long(actual), long(expected), __LINE__, strerror(m_status)); \
            } \
            return m_status; \
        } \
    } while(0)
#define SKIP_PADDING() \
    do { \
        status_t err = skip_padding(); \
        if (err != NO_ERROR) { \
            ALOGD("SKIP_PADDING FAILED at line %d", __LINE__); \
            m_status = err; \
            return err; \
        } \
    } while(0)

    status_t
    BackupDataReader::ReadNextHeader(bool *done, int *type) {
        *done = m_done;
        if (m_status != NO_ERROR) {
            return m_status;
        }

        int amt;

        amt = skip_padding();
        if (amt == EIO) {
            *done = m_done = true;
            return NO_ERROR;
        } else if (amt != NO_ERROR) {
            return amt;
        }
        amt = read(m_fd, &m_header, sizeof(m_header));
        *done = m_done = (amt == 0);
        if (*done) {
            return NO_ERROR;
        }
        CHECK_SIZE(amt, sizeof(m_header));
        m_pos += sizeof(m_header);
        if (type) {
            *type = m_header.type;
        }

        // validate and fix up the fields.
        m_header.type = fromlel(m_header.type);
        switch (m_header.type) {
            case BACKUP_HEADER_ENTITY_V1: {
                m_header.entity.keyLen = fromlel(m_header.entity.keyLen);
                if (m_header.entity.keyLen <= 0) {
                    ALOGD("Entity header at %d has keyLen<=0: 0x%08x\n", (int) m_pos,
                          (int) m_header.entity.keyLen);
                    m_status = EINVAL;
                }
                m_header.entity.dataSize = fromlel(m_header.entity.dataSize);
                m_entityCount++;

                // read the rest of the header (filename)
                size_t size = m_header.entity.keyLen;
                char *buf = m_key.lockBuffer(size);
                if (buf == NULL) {
                    m_status = ENOMEM;
                    return m_status;
                }
                int amt = read(m_fd, buf, size + 1);
                CHECK_SIZE(amt, (int) size + 1);
                m_key.unlockBuffer(size);
                m_pos += size + 1;
                SKIP_PADDING();
                m_dataEndPos = m_pos + m_header.entity.dataSize;

                break;
            }
            default:
                ALOGD("Chunk header at %d has invalid type: 0x%08x",
                      (int) (m_pos - sizeof(m_header)), (int) m_header.type);
                m_status = EINVAL;
        }

        return m_status;
    }

    bool
    BackupDataReader::HasEntities() {
        return m_status == NO_ERROR && m_header.type == BACKUP_HEADER_ENTITY_V1;
    }

    status_t
    BackupDataReader::ReadEntityHeader(String8 *key, size_t *dataSize) {
        if (m_status != NO_ERROR) {
            return m_status;
        }
        if (m_header.type != BACKUP_HEADER_ENTITY_V1) {
            return EINVAL;
        }
        *key = m_key;
        *dataSize = m_header.entity.dataSize;
        return NO_ERROR;
    }

    status_t
    BackupDataReader::SkipEntityData() {
        if (m_status != NO_ERROR) {
            return m_status;
        }
        if (m_header.type != BACKUP_HEADER_ENTITY_V1) {
            return EINVAL;
        }
        if (m_header.entity.dataSize > 0) {
            int pos = lseek(m_fd, m_dataEndPos, SEEK_SET);
            if (pos == -1) {
                return errno;
            }
            m_pos = pos;
        }
        SKIP_PADDING();
        return NO_ERROR;
    }

    ssize_t
    BackupDataReader::ReadEntityData(void *data, size_t size) {
        if (m_status != NO_ERROR) {
            return -1;
        }
        int remaining = m_dataEndPos - m_pos;
        if (kIsDebug) {
            ALOGD("ReadEntityData size=%zu m_pos=0x%zx m_dataEndPos=0x%zx remaining=%d\n",
                  size, m_pos, m_dataEndPos, remaining);
        }
        if (remaining <= 0) {
            return 0;
        }
        if (((int) size) > remaining) {
            size = remaining;
        }
        if (kIsDebug) {
            ALOGD("   reading %zu bytes", size);
        }
        int amt = read(m_fd, data, size);
        if (amt < 0) {
            m_status = errno;
            return -1;
        }
        if (amt == 0) {
            m_status = EIO;
            m_done = true;
        }
        m_pos += amt;
        return amt;
    }

    status_t
    BackupDataReader::skip_padding() {
        ssize_t amt;
        ssize_t paddingSize;

        paddingSize = padding_extra(m_pos);
        if (paddingSize > 0) {
            uint32_t padding;
            amt = read(m_fd, &padding, paddingSize);
            CHECK_SIZE(amt, paddingSize);
            m_pos += amt;
        }
        return NO_ERROR;
    }


} // namespace android
